In a stunning announcement by the United States Environmental Protection Agency (EPA) today, automobile manufacturer Volkswagen was alleged to have purposely programmed certain of its vehicles to circumvent EPA emission standards for air pollutants.

The alleged actions resulted in a Notice of Violation (NOV) in which EPA claims that four-cylinder Volkswagen and Audi diesel cars were designed with software packages that shut off on-board emission control systems unless they sensed that the vehicle was undergoing an official smog test, at which time the software turned the systems on.

During normal vehicle operation, according to EPA, the vehicles operated without emission controls operating as they were legally required to do.

EPA said the ruse went on for several years before it was discovered and covered model years 2009 – 2015.

In a separate action, the California Air Resources Board (ARB) issued an In-Use Compliance letter to Volkswagen. The two agencies have both initiated further investigations into the company’s alleged actions.

The federal Clean Air Act defines such software as a “defeat device.” In this case, EPA alleged that the cars met emissions standards in the laboratory or a testing station, but, during normal driving, Nitrogen Oxide (NOx) emissions increased by 10 to 40 times more than what is allowed.

“Using a defeat device in cars to evade clean air standards is illegal and a threat to public health,” said Cynthia Giles, Assistant Administrator for the Office of Enforcement and Compliance Assurance. “Working closely with the California Air Resources Board, EPA is committed to making sure that all automakers play by the same rules. EPA will continue to investigate these very serious matters.”

“Working with US EPA we are taking this important step to protect public health thanks to the dogged investigations by our laboratory scientists and staff,” said Air Resources Board Executive Officer Richard Corey. “Our goal now is to ensure that the affected cars are brought into compliance, to dig more deeply into the extent and implications of Volkswagen’s efforts to cheat on clean air rules, and to take appropriate further action.”

NOx emissions, when combined with Volatile Organic Compounds (VOC), sunlight, and certain meteorological conditions, such as found here in the San Joaquin Valley, react to form photochemical smog or ozone. Ozone is very harmful to human health and the environment and is one of the main reasons that Valley residents are exposed to harmful air pollution on a daily basis.

The alleged scam was discovered by EPA and ARB as a result of independent testing by West Virginia University researchers who were working with the International Council on Clean Transportation, a non-governmental organization. Volkswagen subsequently admitted this month that the cars contained defeat devices after EPA and ARB demanded an explanation.